Fig. 2471.
Fig. 2472.
Adjustable tongs are made of various forms; thus a simple plan is shown in [Fig. 2470]. The gripping surface of the jaw is shaped as at v, so as to admit varying diameters of pipe, the smaller diameters passing farther up the v, the distance of the end a of jaw, or leg f, being regulated to grip the pipe in the proper place by operating the screw s, which is tapped into the jaw f and pivoted in b, the slot c enabling f to move along b. The capacity of tongs of this design is about three diameters of pipe, as 1, 11⁄4, and 11⁄2 inches. There are various other forms of adjustable pipe tongs, but most of them possess the disadvantage that the adjustable jaw hangs loosely, involving some extra trouble in placing them upon the pipe, because one hand must be employed to guide the loose jaw and adjust its position on the pipe. [Fig. 2471] represents tongs of this class, the gripping size being varied by moving the jaw a upon b at the various notches. The end of b is serrated to afford a firmer grip upon the pipe. [Fig. 2472] represents another adjustable pipe tongs, which is made in two parts, a straight lever a and hooked lever b, the former passing through a slot in the latter. The back of the straight lever is notched and a serrated fulcrum piece c is pivoted in the slotted lever by a pin upon which the lever b receives its support when the tongs are in operation. The fulcrum piece is provided with a spring which retains the serrated edge in proper position to engage the notches in the lever a. By means of the thumb piece d, the piece c can be moved in either direction to increase or diminish the gripping size of the tongs. When the tongs are open the lever a can be moved within the slot and adjusted so that the tongs will fit the pipe. The fulcrum piece c, being pivoted, allows the full length of its serrated edge to come into contact with the corresponding portion of the lever a, so that the parts always have a firm bearing and are subjected to an equal wear.
Fig. 2473.
A common form of pipe tongs of this class is shown in [Fig. 2473], b being pivoted to a by a pin, and changing to various holes in a to suit different diameters of pipe.
Erecting Pipe Work.—In erecting pipe work care must be taken to have it align as true as possible, as well as to have the joints tight enough to stand the required pressure without leakage. If the elbows, tees, or other fittings are not threaded true, a pipe whose thread is not true with its axis may be selected or cut purposely to suit the error in the fitting, so as not to leave an unsightly finish to the job.